The present invention relates to a conveyor or transport mechanism by which devices under test (DUTs) are conveyed or transferred simultaneously from a contact-in stage to a contact or test stage and from the test stage to a contact-out stage in an IC handler or an IC tester.
In a conveyor or transport mechanism of a conventional IC handler, as shown in FIGS. 1A and 1B, a contact-in stage 10A for feeding ICs to be tested, a test stage 10B for testing ICs and a contact-out stage 10C for taking out tested ICs are aligned at equal intervals L, and above them, a contact arm 4 extending in parallel to their alignment is disposed in a manner to be movable from side to side. On the contact arm 4 there are mounted two vertically moving air chuck units 6A and 6B at the distance L from each other. The contact arm 4 travels in a horizontal direction between a first position P1 where the air chuck units 6A and 6B lie just above the contact-in stage 10A and the test stage 10B, respectively, and a second position P2 where they lie just above the test stage 10B and the contact-out stage 10C, respectively. On the contact arm 4 there are mounted air cylinders 8A and 8B, by which the air chuck units 6A and 6B can be driven up and down.
In the conventional IC handlers, DUTs are transferred by repeating such a cycle of operation as shown in FIG. 1C. At first, as shown in FIG. 1A, the contact arm 4 is at the first position P1, where the air chuck units 6A and 6B are lowered by the air cylinders 8A and 8B and suck up an IC 5.sub.2 to be tested from the contact-in stage 10A and a tested IC 5.sub.1 from the test stage 10B, respectively. For convenience' sake, this step will be referred to as step S3. The air chuck units 6A and 6B holding the ICs 5.sub.1 and 5.sub.2 are driven by the air cylinders 8A and 8B back to their upper positions (step S4), after which the contact arm 4 is driven to the left and stops at the second position P2 (step S5).
At the second position P2, as shown in FIG. 1B, the air chuck units 6A and 6B are brought down (step S6) and the tested IC 5.sub.1 held by the air chuck unit 6B is released onto the contact-out stage 10C. At the same time, the IC 5.sub.2 to be tested next is loaded onto an IC socket (not shown) of the test stage 10B and held with all of its pins pressed against corresponding pins of the socket until the end of the test. While the IC 5.sub.2 is tested with its pins fixed by the air chuck unit 6A, an IC 5.sub.3 to be tested next is fed to the contact-in stage 10A. Upon completion of the test, the ICs 5.sub.2 and 5.sub.1 are left on the test stage 10B and the contact-out stage 10C, respectively, and the air chuck units 6A and 6B are returned to their upper positions (step S1), after which the contact arm 4 is brought to the right-hand first position P1 (step S2). In this while, the tested IC 5.sub.1 on the contact-out 10C is taken out therefrom.
At the first position P1, as indicated by the broken lines in FIG. 1B, the air chuck units 6A and 6B are lowered (step S2), then the air chuck unit 6A sucks up thereto the IC 5.sub.3 to be tested next from the contact-in stage 10A and the air chuck unit 6B sucks up thereto the tested IC 5.sub.2 from the test stage 10B. Thereafter, step S3 and the subsequent steps, described above, are repeated.
The time interval from the end of IC test to the beginning of the next IC test will hereinafter be called an index time. The index time in the conventional IC handler is composed of steps S1 through S6 as shown in FIG. 1C, but steps S1, S2 and S3 are performed with no ICs held by the air chuck units 6A and 6B. Because of such lost motion of the air chuck units in the transfer steps of the index time, the prior art conveyor or transport mechanism requires many transfer steps and hence is inefficient in operation; accordingly, much time is needed to test a number of ICs.